Basal Ganglia Disorders

Diagnostic Approaches

The American College of Radiology recommends MRI without contrast, including susceptibility-weighted sequences, as the optimal imaging modality for evaluating basal ganglia disorders due to superior soft-tissue characterization and sensitivity to iron deposition 2
Genetic testing is the diagnostic test of choice for suspected Huntington's disease and should be performed in concert with initial imaging, as MRI findings alone are insufficient for diagnosis 1

Chorea results from dysfunctional basal ganglia-thalamo-cortical circuits, with the most common focal abnormality involving the anterior caudate and putamen (60% of cases), as seen prototypically in Huntington's disease 1
Huntington's disease is characterized by progressive loss of GABAergic medium spiny neurons in the striatum with disproportionate neostriatal volume loss 1
Wilson's disease involves structural abnormalities in basal ganglia with simultaneous involvement of basal ganglia, thalamus, and brainstem (55.3% of cases) being highly specific 1

The "eye-of-the-tiger sign" (T2 hyperintensity within hypointense globus pallidus) is pathognomonic for Neurodegeneration with brain iron accumulation (NBIA) type 1, though it may not be present in all cases or may change over time 2
Diffusion-weighted and T2-FLAIR sequences are most sensitive for detecting basal ganglia abnormalities in chorea evaluation 1
Abnormal thalamo-cortical connectivity patterns can be demonstrated in movement disorders, with thalamo-prefrontal hypoconnectivity indicating dysfunction of motor inhibition 1